Selection Of Salt Tolerant Cynodon Richard Plants

Bermuda grass (Cynodon dactylon) is one of the most widely used warm-season turfgrasses with the highest score,salt resistance,fast growth,and the advantage of quick turf establishment. Twenty one salt-tolerant germplasm materials were preliminarily selected from 403 Bermuda grass(Cynodon dactylon)after the salt tolerance treatments conducted in Hoagland's nutrient solution culture with the salt concentration adjusted with chemically pure NaCl. These 21 salt-tolerant germplasm materials were selected again at different salt concentration gradients, their physiological and biochemical reactions under salt stress were observed and new Bermuda grass breeding materials were obtained. The results are as follows:(1) Twenty one salt-tolerant germplasm materials were survived with 2.6% NaCl concentration in the nutrient solution, preliminarily selected from the 403 Bermuda grass (Cynodon dactylon) germplasms treated with 2.0%,2.6%,3.1% (mass percent solution) NaCl concentration adjusted by chemical pure NaCl.(2) Through second screening at the different concentration gradients, the study on the physiological and biochemical characteristics of 21 germplasms under salt stress was conducted. The results showed that the salt injury symptoms increased, leaf color changed from green to yellow, leaf tips and leaf margins wilted due to water loss with the salt concentration and treatment time increased, and finally plants were scorched to death. The plants showed no salt injury or just light salt injury after salt treatment of 2.2% NaCl concentration for 30 days, moderate or severe salt injury after salt treatment of 2.5% NaCl and 10 germplasm materials (first class of salt tolerance) died at the NaCl concentration of 2.8%, and the 11 germplasm materials remained alive (second class of salt tolerance), but the salt injuries had reached severe or extreme. All germplasm materials died at the NaCl concentration of 3.0%.(3) With the salt concentration increased, plant growth was inhibited or stopped and there was a sharp decline in the growth of plant height; cell membrane permeability increased, leakage of electrolytes occurred and the relative conductivity increased; chlorophyll content decreased; the content of free proline gradually increased at the low concentrations of NaCl, reached a peak when the NaCl increased to a certain level and decreased gradually then; MDA content increased; Overall, POD activities increased first and then decreased, but that of the A404 and A71 decreased; the overall SOD activity increased, but that of the A341, A404 and A405 increased at first and then decreased. (4) The conclusion was obtained after the comprehensive analysis of each indexes, that the greater height of plant growth, the lower the relative conductivity, the higher chlorophyll content, the more proline accumulated, the higher POD and SOD activity, less MDA content, then the more salt tolerance of Bermuda grass. In this study the descending order of the salt tolerance of Bermuda grass germplasms are as follows:Hainan A278> Hainan A71> Hainan A251> Hainan A286> Zhejiang A158> Hainan A417> Thailand A172> Hainan A384> Hainan A207> Hainan A 195> Zhejiang A 120> Zhejiang A 157> Guangdong A398> Hainan A404> Hainan A405> Fujian A200> Hainan A260> Hainan A300> Shandong A38> Guangdong A213> Hainan A341.